Yeah, I'm saying they shouldn't, but plenty of them do. They use geoip or location services to work out where you are and then use that to send you to the local site or the site in the language that they feel is appropriate for that location.

If you're really lucky they then make it difficult (and sometimes practically impossible) to switch.

Besides the problem you've highlighted for countries with multiple languages, you also have immigrants, people on holiday, multilingual people, VPN users... And it's not great for your SEO either.